net: phy: use mii_10gbt_stat_mod_linkmode_lpa_t in genphy_c45_read_lpa

Use mii_10gbt_stat_mod_linkmode_lpa_t() in genphy_c45_read_lpa() to
simplify the code.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>